SCM for Android Developers Using Git
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Git is a free and open source distributed version control system. It allows developers to work in parallel, merge code branches, and protect against mistakes with the ability to revert changes. Git uses SHA1 hashes to uniquely identify commits and makes it very difficult for commits to be tampered with. Common Git commands include add, commit, log, blame, checkout, reset, stash, amend, revert, push, pull, fetch, tag, and bisect. Branching allows controlling feature sets through topic branches, and merging or rebasing changes back into the mainline.
SCM for Android Developers Using Git
- 1. Git For the Android Developer AnDevCon 2011 : Tony Hillerson #AnDevCon #effectiveui http://www.slideshare.net/thillerson/scm-for-android-developers-using-git
- 2. About Me • Worked with Android and Git for a few years now • O’Reilly Screencaster: Developing Android Applications • http://training.oreilly.com/androidapps/ • http://training.oreilly.com/androidapps2/ • Tech Reviewer:
- 3. Preliminaries Getting Git and Getting Set Up
- 4. What’s a Git? A completely ignorant, childish person with no manners. - http://urbandictionary.com Linus Torvalds http://en.wikipedia.org/wiki/Linus_Torvalds
- 5. What’s a Git? Git is a free & open source, distributed version control system designed to handle everything from small to very large projects with speed and efficiency. - http://git-scm.com
- 6. Getting Set Up on Mac • Homebrew - http://mxcl.github.com/homebrew/ • MacPorts - http://www.macports.org/
- 7. Getting Set Up on Windows • msysgit -http://code.google.com/p/msysgit/ • Cygwin - http://www.cygwin.com/
- 8. Getting Set Up on Linux • apt, etc - you probably know the drill
- 9. Gooies! • Git Tower - http://git-tower.com M • Brother Bard’s GitX fork - Mac http://brotherbard.com/blog/2010/03/experimental-gitx-fork/ A C • Tortoise Git - http://code.google.com/p/tortoisegit/ W Mac I N
- 11. Reference • Git - http://git-scm.com/ • ProGit - http://progit.org/book/ - Scott Chacon • Insider Guide to Github - http://www.pragprog.com/screencasts/ v-scgithub/insider-guide-to-github - Scott Chacon
- 12. Note • Code may be in backticks: `git <command>` • Don’t input the backticks
- 13. The Command Line A Short Sermon
- 14. Seven Use Cases Where Git will Make your Life Easier
- 15. Project History Git will Make your Life Easier
- 16. Why Source Control • For the solo developer? • Protection against mistakes • Freedom • to refactor • to experiment • For the development team? • All of the above, plus: • Parallel development • Merging different code branches
- 17. Simple Commands • `git init`- Creates an empty Git repository • .gitignore - tells git to ignore certain files • `git add` - Adds a file to the stage (“stages a file”) • `git rm` - Removes from version control • `git commit` - Commits the staged changes to the (local) repository • `git log` • `git add -i` Interactive Add
- 18. git git or clone init git 86650c185eda50c9f9d58e2fbdf8b7113e5dee54 git commit changes add git git commit 6facfd9f34173f4fb024196996e948a87c85eb56 changes add git git commit b02ef5bf190e28ba24eab3ffab6133181cb5b5ef changes add ... ∞ Simple Workflow
- 19. .gitignore • Can be nested deeply • https://github.com/github/gitignore • Use it! Contribute!
- 20. Git Log - The Project’s History • What got committed? • Commit messages • Content • When? Who?
- 21. What’s With all the Characters? 86650c185eda50c9f9d58e2fbdf8b7113e5dee54 • SHA1 Hash • Uniquely identifies a commit • Secure - very unlikely that someone can tamper with content in a repository “... to have a probability of a SHA1-hash collision rise to 1/2, you need about 10^24 objects ...” - Scott Chacon in Pro Git (paraphrased)
- 22. Interactive Add - Building Commits • `git add` simply adds to the stage • `git commit -a` will commit all changes to tracked files (add and commit) • `git add -i` -- a command line tool to interactively add changes • Individual commits shouldn’t leave things broken • Try to commit some useful feature or bug fix all together
- 23. Getting Out of Trouble Git will Make your Life Easier
- 24. Advanced Commands • blame • checkout • commit -a • reset • stash • commit --amend • revert
- 25. git blame • remember: git help blame • Who broke the build??? etc...
- 26. git checkout, commit -a, reset • remember: git help reset • `git commit -a` = commit bypassing `git add` • `git checkout <filename>` = remove all unstaged changes • `git reset <filename>` = opposite of `git add <filename>` • `git reset HEAD` = same as above - acts on all changes • `git reset HEAD^` (also ^^, or ~1, ~42, etc.) = rollback commits to working tree • `git reset --soft` = rollback commit to stage
- 27. git stash • remember: git help stash • Stash away changes in a safe place
- 28. git commit --amend • Oops! I misspelled something in the commit message • Oops! I did `git commit -a` and forgot to `git add` a file • Oops! I just committed a bug • USE ONLY BEFORE YOU SHARE CHANGES
- 29. git revert • Commits the reverse of a commit • The previous commit is still there • != svn revert
- 30. Collaboration Git will Make your Life Easier
- 31. Remotes • remote add • push • clone • pull • fetch
- 32. Strategies • Star • Peer to Peer • Blessed Repository • Hierarchical
- 33. Committer Committer Committer “The Committer Server” Committer Committer Star
- 34. • ssh://user@computer:path/to/repo.git • http Peer • Gitosis • Gitolite Peer Peer Peer to N Peers
- 35. Dictator ... etc. Maintains a “blessed repository” Lieutenant Lieutenant Developer Developer Developer Developer Hierarchical (Linux model)
- 36. Topical Development Git will Make your Life Easier
- 37. Branching • checkout -b • merging • Rebasing • cherry-pick
- 38. How To Think About Branching • Topic Branches • Mainline • What do you want “master” to mean? • Branching examples
- 39. Topic Branches • Branching is about controlling feature sets • Make a new branch for a story • Make a new branch for a bug fix • Make a new branch to spike something
- 40. Team Branching Strategies • What do you want “master” to mean? • Keep master deployable? • one strategy for web software • Use “master” as an integration branch? • Each developer uses topic branches and integrates to master • Make a branch for releases
- 41. Branching git checkout -b add_login_activity master Mac fb4f5d9 c5083fa add_login_activity Mac 9aa8827 fe594ce ccb6f5e
- 42. Branching: Merging git checkout master git merge add_login_activity master Mac 9aa8827 fe594ce ccb6f5e fb4f5d9 c5083fa 3f43fa3 add_login_activity Mac 9aa8827 fe594ce ccb6f5e
- 43. Branching: Rebasing master Mac fb4f5d9 c5083fa 3f43fa3 add_login_activity before Mac 9aa8827 fe594ce ccb6f5e master Mac fb4f5d9 c5083fa 3f43fa3 add_login_activit after Mac 9aa8827 fe594ce ccb6f5e `git rebase master`
- 44. Branching: Rebasing • Better than merging • Don’t use if you’ve pushed your branch to a remote • Git will complain about refs • Can override with `git push -force` • Also available on `git pull --rebase` • Helpful for avoiding merge commits • May cause problems if git can’t automatically merge • `git reset HEAD` and start over with normal `git pull`
- 45. Cherry-pick git cherry-pick fe594ce A new commit master with the changes from fe594ce Mac fb4f5d9 c5083fa 3f43fa3 add_login_activity Mac 9aa8827 fe594ce ccb6f5e
- 46. Cherry Picking • Doesn’t add a reference to the old commit • Only applies the changes • Future merges should apply cleanly
- 47. Release Management Git will Make your Life Easier
- 48. Tagging • tag • push --tags
- 49. Tagging git tag -a -m"Tagging v1.0" v1.0 c5083fa master Mac fb4f5d9 c5083fa 3f43fa3 • Both -v1.0 and c5083fa will point to c5083fa • Push this tag with `git push --tags` • Can be cryptologically signed
- 50. Bug Fixing Git will Make your Life Easier
- 51. Bug Fixing • blame • bisect
- 52. Bisect git bisect start HEAD git bisect bad fb4f5d9 Mac c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb git bisect good fb4f5d9 HEAD fb4f5d9 Mac c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb git bisect good Git tells you this was the git bisect good first bad git bisect bad commit HEAD fb4f5d9 Mac c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb
- 53. Open Source Code Git will Make your Life Easier
- 54. Github.com • Search it! • Forking • Pull Requests
- 55. Thank you! Git For the Android Developer AnDevCon 2011 : Tony Hillerson